Historically kinetic energy penetrators have been fired from tank guns where the launch accelerations are in the magnitude of 50,000 g's. A penetrator diameter of approximately one inch is required to withstand these high launch accelerations; however, the diameter does not contribute to armor penetration as penetration is primarily dependent upon penetrator length. Therefore, the most weight efficient kinetic energy penetrator is one of required length to penetrate a given target and of minimum diameter. In order to decrease the diameter to a minimum the launch accelerations must be reduced, which can be achieved by reducing total weight and by utilizing a kinetic energy penetrator rocket system. Since the penetrator weight is proportional to the square of the diameter a one-half inch diameter penetrator will decrease the total penetrator weight by a factor of four of a one-inch penetrator. The reduction in penetrator diameter and weight allows for the use of a rocket with lower launch accelerations than those of guns, yet maintaining the length of the present one-inch diameter penetrator. This invention uses a plug nozzle and a weight efficient structure which contributes to reducing total weight and launch level acceleration requirements. The plug nozzle kinetic energy penetrator rocket described in the present invention can be used as an unguided weapon or as a kinetic energy penetrator test vehicle.